In a process of manufacturing semiconductors or magnetic disks, use is made of a charged particle beam applied apparatus to perform measurement, defect review, inspection or the like of a specimen through observation that includes illuminating the specimen with a charged particle beam (hereinafter, referred to as a signal-detection beam), such as an electron beam and an ion beam, detecting produced secondary charged particles, such as secondary electrons, and performing arithmetic computations on signals obtained from the detected secondary charged particles.
Many of these charged particle beam applied apparatuses employ a technique of scanning a focused charged particle beam on a specimen; however, this technique requires a long time for inspecting the entire surface of the specimen, and therefore improvement of the specimen processing speed is an important issue. In order to resolve the issue, a multi-beam type charged particle beam applied apparatus has been proposed that simultaneously illuminates created multiple signal-detection beams, that is, multiple beams for signal detection, onto a specimen and detects secondary charged particle signals. Such a multi-beam type apparatus using multiple signal-detection beams can enhance the speed for processing the specimen in comparison with apparatuses using one signal-detection beam. For example, Patent Literature 1 proposes a multi-beam type charged particle beam applied apparatus in which a charged particle beam emitted from a charged particle source illuminates a plate (hereinafter referred to as an aperture array) with multiple apertures, the charged particle beam is split by the aperture array into multiple charged particle beams, and the individual split beams are focused by lenses aligned in an array (hereinafter referred to as a lens array).
In addition to the improvement of the specimen processing speed, these charged particle beam applied apparatuses are required, as an important issue, to improve the accuracy of defect detection and measurement in accordance with the increase in miniaturization and complexity of devices. The accuracy of defect detection and measurement depends on the detection accuracy of the secondary charged particles. Since the detection accuracy of the secondary charged particles is greatly influenced by the charge on the surface of the specimen, control of the charge on the surface of the specimen is critical to improve the accuracy of defect detection and measurement. For example, Patent Literature 2 proposes a charge controlling method in which a specimen is illuminated with an electron beam emitted from an electron source for pre-charge, which is separately provided from an electron source for signal-detection beams. However, an electron optical column provided with the electron source of signal-detection beams and an electron optical column provided with the pre-charge electron source have specified dimensions, respectively, that make it difficult to shorten the distance between the positions illuminated by the electron sources. The distance makes a fairly long time difference between the pre-charge beam illumination for controlling charge and the signal-detection beam illumination. Owing to the time difference, some specimens may not be able to maintain their charge provided by the pre-charge beam until the signal-detection beam illuminates the specimens.
In order to address the problems, Patent Literature 3 proposes a multi-beam type electron beam inspection apparatus that uses a part of produced multiple beams for controlling charge. In this method, a charge-control beam (primary charge-control beam) and a signal-detection beam (primary inspection beam) are simultaneously formed from an electron source by using an aperture array and lens array. The representations in the brackets are terms used in Patent Literature 3.
According to Patent Literature 3, in comparison with the method in which the pre-charge electron source is separately provided from the electron source for signal-detection beams, the positions illuminated by the charge-control beam and the signal-detection beam can be brought nearer to each other, thereby reducing time from the charge-control beam illumination to the signal-detection beam illumination. This time reduction allows the signal-detection beam to illuminate the specimen, which cannot hold the charge for a long time, before charge attenuation occurs, which improves inspection accuracy. In addition, in order to individually set the illumination conditions of the charge-control beam and signal-detection beam, electrodes used for controlling the charge are separately provided.
Citation List
Patent Literature
    PTL 1: JP-A No. 2007-317467    PTL 2: JP-A No. Hei10 (1998)-294345    PTL 3: JP-A No. 2008-165990